Light-emitting elements (organic EL elements) including organic compounds and utilizing electroluminescence (EL) have been put to more practical use. In the basic structure of such a light-emitting element, an organic compound layer containing a light-emitting substance (an EL layer) is provided between a pair of electrodes. By voltage application to this element, light emission from the light-emitting substance can be obtained.
Since such light-emitting elements are of self-light-emitting type, light-emitting elements have advantages over liquid crystal displays when used as pixels of a display in that visibility of pixels is high and backlight is not required. Thus, light-emitting elements are suitable as flat panel display elements. A display including such a light-emitting element is also highly advantageous in that it can be thin and lightweight. Besides, very high speed response is one of the features of such an element.
Since light-emitting layers of such light-emitting elements can be successively formed two-dimensionally, planar light emission can be achieved. This feature is difficult to realize with point light sources typified by incandescent lamps and LEDs or linear light sources typified by fluorescent lamps. Thus, light-emitting elements also have great potential as planar light sources, which can be applied to lighting devices and the like.
Although displays or lighting devices including light-emitting elements can be suitably used for a variety of electronic devices as described above, their performance and cost competitiveness have plenty of room to improve. In order to achieve this, materials that have good characteristics and are easily handled are required. There are particularly great demands on heat resistance and reliability such as a lifetime.
Patent Document 1 discloses a pyrimidine- or triazine-based derivative, an electron-transport material containing the same, and an organic electroluminescent element containing the same.